Generally, implants are used in dental surgery or in bone surgery to reconstruct teeth or bone parts of a human being. Usually, implants are intended to be inserted by screwing or pressing into a receiving bore which has been prepared e.g. in the bone tissue. The preparation consists of a conventional surgical procedure. For applications in the dental sector, usually an incision is made along the gingival tissue at the position where the implant is going to be inserted. Successively, a cylindrical bore is drilled into the bone tissue in order to insert the implant therein.
Implants are mostly provided with a holding element, which usually is fixedly secured to them by a screw or through screwing, and in this case the holding element is provided with an external screw thread.
A holding element for implants can be employed during a number of different production phases of implants, while preparing them for a surgical intervention, and directly during implantation. One primary application of the holding element is to provide the option of attaching a handhold in order not to touch the implants directly and in this manner to keep them sterile. Another application of holding elements is to offer the option of attaching manipulating members thereto for further processing of the implant. This facilitates the handling of the implants even during their production.
In case of an implantation, the holding element permits to extract the implant from a sterile container, for example an ampule, and to implant it without direct contact with contaminating agents by means e.g. of a manipulating tool gripped to the holding element and through the holding element gripped to the implant itself. By operating only on the manipulating tool, the implant is transferred from the sterile sleeve to the site of use and is implanted therein without being directly touched.
Once the implant is driven to the desired depth in the bone tissue, the manipulating tool is removed, leaving the holding element fixedly resting on the implant. To remove the holding element an unscrewing force, e.g. through an unscrewing spanner, must be applied on the assembly composed of holding element and implant. This operation requires generally an amount of space which often is not available. Moreover, if the implant has been placed in particular in soft bone, the torque applied to remove a holding element may also lead to unscrew the entire assembly or to damage the implant surface/bone tissue interface. Transferring unwanted forces to the bone may cause necrosis of the interface bone tissue, and consequently mobilization of the implant may occur.
In order to avoid the negative effect of the unscrewing force, in these kind of implant systems, a counter torque tool is used, if possible, to prevent the torsional force transfer to the implant when the holding element is unscrewed and removed, depending on the implant structure and on the free space available at the implantation site.
U.S. Pat. No. 6,206,696 discloses a delivery system for implants of the above mentioned kind, comprising a dental implant and a holding element composed of a driving tool and a healing screw. The driving tool is designed to engage the healing screw in order to drive the implant during implantation. For this purpose it has an engagement feature which permits to simply hook or unhook from the healing screw.
The dental implant system disclosed by U.S. Pat. No. 6,206,696, does not offer the possibility to control the force applied during implantation and particularly while screwing in the implant, so that if a too strong force is applied, the thread of the healing screw may cant in the thread of the implant. After the healing period is completed a prosthesis has to be affixed.